I have a 2009 Mercedes c63 so on January 15 I hit my bumper on the passenger lower side and then on January 18 i noticed coolant missing without any leaks and everytime it would be missing I would add it, I also always checked inside the coolant and it looked fine just needed more coolant so I added it and I always checked the dip stick for any contamination or mixing or milky oil and never ever found that. So I continued to drive the car and it was fine never misfired never had a rough idle never had white smoke out the exhaust. And I did around 1k miles like that then on February 7th brought the car for a oil change to look at the oil and it looked perfectly fine. So I still continued to drive it. Then on February 16 I brought the car to a shop to do a pressure test and after that pressure test the shop notified me that it didn’t have a external leak and that they said it’s internal, they checked the oil level and it was high. So the next day I told them to do an oil change and there was 7 liters of coolant inside oil pan. They drained alll the coolant inside the oil pan and also all the oil and put new oil inside.

 

So more than likely a head bolt has broken and compromised the head gasket

 

my thing is the car was loosing coolant for a month I drive the car hard still and never ever noticed in that month that the oil looked weird or a miss fire or anything weird never ever over heated. My thing is if it was the head bolts the whole time why want the oil looking weird when I did a oil change after a month of loosing coolant and driving hard?

 

whats that for stuff ?

Agree - old rusty head bolts.

 

my thing is the car was loosing coolant for a month I drive the car hard still and never ever noticed in that month that the oil looked weird or a miss fire or anything weird never ever over heated. My thing is if it was the head bolts the whole time why want the oil looking weird when I did a oil change after a month of loosing coolant and driving hard?

 

You said they did a pressure test..I'm assuming the cooling system? More than likley the added pressure was finally enough to blow the head gasket that was already compromised due to bad head bolts.

Until you fix it properly, you're driving a ticking time bomb.

 

but how do I was driving it hard and pushed the car and never noticed any coolant in the oil?

 

This type of thing can be a progressive failure. Letting loose, letting more loose. Loose. Head gasket leaking a tiny bit, then more, then a lot more, (for example).

 

this. And once one goes it puts more pressure on the remaining. You can have one fail and no gasket failure. If another one begins to losen or break you get a complete failure. It's not a set failure to outcomes. You can get coolant leaking into cylinders and not the oil. You can get leaks into the oil and not the cylinders. You can have oil leaks and no coolant depends on the engine design and failure point

 

i understand that’s how the head gasket works slowly over time. But how can I lose a bottle and a half of coolant and after doing 1k miles with a coolant issue and do an oil change after the oil looks perfect fine? To lose a bottle and a half of coolant and never notice any over heating issues never noticed white smoke never noticed any issues?

 

It takes a lot of coolant mixed into the oil for a person to "notice" this.

If you extracted a sample of the current fill and sent it in for an oil analysis, chances are the results would show an obvious sign of coolant mixed in regardless of how clean the oil looks to you.

The fact that 7L of coolant was drained out with the oil recently also tells you everything you need to know.

 

a lot of coolant was lost around a bottle and a half was lost before the first oil change. And then after the pressure test that’s where we finally noticed coolant in the system car was never started after the test

 

Well pop the valve covers off and have a look at the head bolts. Betting you are least 1 is completely failed. Coolant is sticky and will still be in your bearings/lower engine pan area so once you fix your problem you should do a few oil changes to help flush the remaining out. Usually get it up to temperature so it will help some of it vaporize and being heavier than the motor oil it will be at the bottom of the pan when you drain it

 

you think if I do a combustion test it would be able to tell me if the head bolts are bad or a head gasket?

 

I could if you have some leaking from the gasket around one of the cylinders. I've seen head gaskets fail and no combustion issues although he m156 usually does have coolant or oil enter the cylinder with a bolt or gasket failure. Worth a shot

 

will try doing that when I go pick the car up from the shop, im still generally confused on how the car was driven hard for a month did 1k miles lost about a bottle and a half of coolant and the oil was NEVER milky and was never overheating but when I did a oil change it was completely normal oil

 

It doesn't have to be a headbolt, however it most likely is. Other possibilities are O-rings/silicone that seal the front cover to the block where coolant passes through, a crack in the block or a crack in a cylinder head. You wont know what it is until teardown. The shock and awww that something can go 1000 miles without huge problems is simply from lack of experience. This is pretty normal in the vehicle repair world. People that are even mildly observant pick up on problems very early. As I've stated in dozens of threads complete real catastrophic head bolt failures are far and few. They are pretty much never happen to someone actually trying to take car of their car. They pretty much always start like yours. Low coolant light, think little of it. Top it off. A month or 2 later coolant light comes back on. No signs of external leakage. This is where you are. This is when a normal person goes hmmm I think i have a leak or problem maybe I should get it looked at. This is when the neglect continues. Mercedes aren't cheap to repair especially AMG's. Maybe it will heal itself lol. Keep driving....From there the coolant light comes on in the next 2-3 weeks. Top it off again seems totally normal... Within a week coolant light is back on. Top off again... A few days later you'll get a misfire. hmmmm check engine light. Throw a coil and spark plug at it... Top off again... Keep driving, keep topping off daily. This is totally normal nothing to see here. Bam! finally you get what you wanted a bent rod from a head bolt / head gasket failure. Tow it to a local mechanic and get quoted $10k+ to replace the motor with a questionable salvage yard pull out rather than a head bolt / head gasket job (roughly $4k depending on what additional items should also get replaced preventatively while you're in there)